Efficient Inductive Power Transfer Research Articles

Design of Inductive Power Transfer Charging System with Weak Coupling Coefficient

Inductive power transfer (IPT) technology is used in various applications owing to its safety features, robust environmental adaptability, and convenience. In some special applications, the charging pads are required to be as compact as possible to accommodate practical spatial requirements, and even size requirements dictate that the diameter of the charging pad matches the air gap. However, such requirements bring about a decrease in the transmission efficiency, power, and tolerance to misalignment of the system. In this paper, by comparing a double-sided inductor–capacitor–capacitor (LCC), double-sided inductor–capacitor–inductor (LCL), series–series (SS), and inductor–capacitor–capacitor–series (LCC-S) compensation topologies in IPT systems, we identified a double-sided LCC compensation topology that is suitable for weak coupling coefficients. Furthermore, this study modeled and simulated the typical parameters of coreless coils in circular power pads, such as the number of coil layers, turns, wire diameter, and wire spacing, to enhance the mutual inductance of the magnetic coupler during misalignment and long-distance transmission. A wireless charging system with 640 W output power was built, and the experimental results show that a maximum dc-dc efficiency of over 86% is achieved across a 200 mm air gap when the circular power pad with a diameter of 200 mm is well aligned. The experimental results show that using a suitable compensation topology and optimizing the charging pad parameters enables efficient IPT system operation when the coupling coefficient is 0.02.

Design of a High–Efficient IPT System for Battery Charging Under CP-CV Charging Scenarios

Maintaining high efficiency and controlling output voltage with variable load is challenging for inductive power transfer (IPT) based battery charging systems. In addition, choosing the proper charging scenarios simultaneously with the battery's equivalent load variation significantly improves the charging rate. This paper proposes a semi-active rectifier (SAR) battery charging system on the basis of a series-series resonant IPT system using constant-power (CP) and constant-voltage (CV) charging modes. A novel control approach based on the adaptive selection of the operating frequency of IPT and the conduction angle of the SAR is used to achieve high efficiency in CP-CV modes. The inverter and the SAR are both capable of soft switching. Furthermore, considering the same maximum power in CP and constant-current (CC) modes, the CP mode offers more charging rate with less destructive effects. The proposed control strategy has been simulated, and a prototype system is implemented to show the high-efficiency performance of the system during CP-CV modes.

Three-Leg DC–DC Converter for Efficient Inductive Power Transfer of Electric Vehicles for Wide-Range Battery Applications

The design of an inductive power transfer system for different electric vehicle (EV) models with widely varied battery pack voltages has been a challenging task. The majority of modern EV models are equipped with 400 V or 800 V battery packs. To charge both batteries efficiently, an additional DC-DC converter on the receiver side is employed, which reduces the overall system efficiency and also increases the cost. This article proposes a reduced switch count novel converter to charge distinct EV models without degrading the efficiency of the system. The proposed converter has two operating modes, a voltage doubler mode to charge an 800 V battery and a current doubler mode to charge a 400 V battery at the same power level. MATLAB/Simulink simulations have been carried out to verify the performance of the 3-leg converter for both 400 V and 800 V batteries at 7.2 kW. Furthermore, a laboratory prototype of the proposed converter for 500 W has been built using the SiC devices, and the results obtained are provided.

Design of a Highly Efficient 20-kW Inductive Power Transfer System With Improved Misalignment Performance

Due to the urgent desire for a fast, convenient, and efficient battery charging technology for electric vehicle (EV) users, extensive research has been conducted into the design of high-power inductive power transfer (IPT) systems. However, there are few studies that formulate the design as a multiobjective optimization (MOO) research question considering both the aligned and misaligned performances and validate the optimal results in a full-scale prototype. This article presents a comprehensive MOO design guideline for highly efficient IPT systems and demonstrates it by a highly efficient 20-kW IPT system with the dc–dc efficiency of 97.2% at the aligned condition and 94.1% at 150-mm lateral misalignment. This achievement is a leading power conversion efficiency metric compared to IPT EV charging systems disseminated in today’s literature. Herein, a general analytical method is proposed to compare the performances of different compensation circuits in terms of the maximum efficiency, voltage/current stresses, and misalignment tolerance. An MOO method is proposed to find the optimal design of the charging pads, taking the aligned/misaligned efficiency and area/gravimetric power density as the objectives. Finally, a prototype is built according to the MOO results. The charging pad dimension and total weight, including the housing material, are 516*552*60 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> /25 kg for the transmitter and 514*562*60 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> /21 kg for the receiver. Correspondingly, the gravimetric, volumetric, and area power density are 0.435 kW/kg, 581 kW/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , and 69.1 kW/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , respectively. The measured efficiency agrees with the anticipated value derived from the given analytical models.

Inductive Power Transfer System With Maximum Efficiency Tracking Control and Real-Time Mutual Inductance Estimation

To design simple and efficient inductive power transfer (IPT) systems, a minimum number of conversion stages and an effective maximum efficiency tracking (MET) are the primary design criteria. The MET control uses a fast mutual inductance estimation (MIE) algorithm to achieve fast tracking of the maximum efficiency point, especially when the variation of the gap distance and misalignment of the magnetic coupler are significant. The feedback control of the MET-MIE IPT system should be designed without a wireless communication channel to improve stability and robustness. In this article, a novel MET-MIE control strategy is proposed for achieving simplicity and high efficiency in IPT systems. Verifications are provided by simulations and experiments. It is shown that maximum efficiency can be tracked with less than 4&#x0025; error in MIE under significant variation of the gap distance and misalignment of the magnetic coupler.

Dynamic Wireless Charging for Inductive Power Transfer Systems in Electric Vehicles

The charging plate creates magnetic fluxing. The charging plate and the adjacent coil can induce current without any contact. By the new trends, wireless charging got more social attention to the outside world as an alternative method for primitive wired charging. Even though wireless charging was implemented to various electronics industries, it is still proven that wired charging is faster than the wireless. But can make the gadget hot, which may not be good for the battery efficiency. The wireless charging does not degrade the battery. A vehicle that is powered by an electric motor rather than a typical petrol or diesel engine is referred to as an electric vehicle. The electric motor is powered by rechargeable batteries. In this article, the dynamic wireless charging of electric vehicles introduces a new methodology of charging even when the vehicle is in motion. The dynamic wireless charging is proposed to allow power transfer to the electric vehicles when they are in motion. Multiple inductive pads should be buried under the roadways. The inductive pads should be energized by a power supply. The track which is dedicated for the wireless charging should have enough distance so that the vehicles can charge up to a stable value until they leave the charging track. This proposed methodology reduces unnecessary time wastage for charging of vehicles. Hardware results obtained the primary pads mounted on road and power supply for primary roads. Besides, it will flow the efficient inductive power transfer and time saving opportunity.

An Efficient Inductive Power Transfer Topology for Electric Vehicle Battery Charging

Recently available high-frequency power converter topologies for inductive power transfer (IPT) system utilize either zero voltage switching (ZVS) or zero current switching (ZCS) based power electronic converters while maintaining a near sinusoidal current for limited power transfer range. However, achieving ZVS or ZCS for all power switches simultaneously is still a challenging task in IPT systems. In this article, an improved zero-voltage zero-current switching (ZVZCS) IPT topology and its switching pattern are proposed. ZVS is achieved by optimizing the classical series compensation and additionally, an auxiliary network is employed to achieve ZCS. The proposed concept is verified by using MATLAB/Simulink based simulations for resistive and battery load. Finally, the practical viability of the proposed topology is validated by the results obtained using a laboratory prototype rated for 1.1 kW, 85 kHz. An efficiency of 91.26% is achieved with ZVZCS for a full dynamic power transfer range of 20 W–1.1 kW.

Compact pulse position control‐based inverter for high efficiency inductive power transfer to electric vehicle

A compact high efficient inductive power transfer (IPT) topology based on pulse position control is proposed for wireless charging of electric vehicle. Near-field wireless charging is efficiently achieved by the resonance-enhanced IPT technique. The system sustains high power transfer efficiency under contingency in misalignment of pickup coil and load variations. The performance evaluation of the proposed system under the occurrence of anticipated perturbation in load and mutual inductance is studied numerically. Experimental results from the developed prototype corroborate the theoretical and simulated results discussed in the proposed study.

Class-E Half-Wave Zero dv/dt Rectifiers for Inductive Power Transfer

This paper analyses and compares candidate zero dv / dt half-wave Class-E rectifier topologies for integration into multi-MHz inductive power transfer (IPT) systems. Furthermore, a hybrid Class-E topology comprising advantageous properties from all existing Class-E half-wave zero dv / dt rectifiers is analyzed for the first time. From the analysis, it is shown that the hybrid Class-E rectifier provides an extra degree of design freedom that enables optimal IPT operation over a wider range of operating conditions. Furthermore, it is shown that by designing both the hybrid and the current-driven rectifiers to operate below resonance provides a low deviation input reactance and inherent output voltage regulation with duty cycle allowing efficient IPT operation over wider dc load range than would otherwise be achieved. A set of case studies demonstrated the following performances: First, for a constant dc load resistance, a receiving end efficiency of 95% was achieved when utilizing the hybrid rectifier, with a tolerance in required input resistance of 2.4% over the tested output power range (50–200 W). Second, for a variable dc load in the range of 100–10%, the hybrid and current-driven rectifiers presented an input reactance deviation less than 2% of the impedance of the magnetizing inductance of the inductive link respectively and receiving end efficiencies greater than 90%. Third, for a constant current in the receiving coil, both the hybrid and the current-driven rectifier achieve inherent output voltage regulation in the order of 3% and 8% of the nominal value, respectively, for a variable dc load range from 100% to 10%.

Development of a 60 kHz, 180 kW, Over 85% Efficiency Inductive Power Transfer System for a Tram

Conventional contact-based train power transfer systems have high maintenance costs and safety issues and cause noise and additional aerodynamic drag. Instead of the conventional system, a loosely coupled online wireless power transfer (WPT) system for a train is proposed in this paper. The operating frequency of the proposed design is 60 kHz to ensure a low flux density and a high-efficiency system with a large air gap. In addition, a new transmitter track and pick-up geometry for 60 kHz operation are designed using finite element analysis (FEA). The proposed design is evaluated theoretically and experimentally. By using the simulated results, a new 180 kW, 15 m test-bed for a tram is constructed. The total power transfer efficiency is greater than 85% at the rated output power, and the loss distribution in the system is identified. Electromagnetic field (EMF) radiation and the voltage induction at the rail are measured for safety evaluation. The measured EMF satisfied international guidelines.

Design of a Current-Source-Output Inductive Power Transfer LED Lighting System

Inductive power transfer (IPT) light-emitting diode (LED) lighting systems have many advantages in commercial, industrial, and domestic applications. Due to the large leakage inductance, primary and secondary capacitor compensations are necessary to improve the power transfer capability. To offer a direct current source output for LED driving, topology with series–series (SS) compensation is chosen and analyzed in this paper. Using a properly designed operating frequency, the SS compensation can be the best topology for the voltage-source-input and current-source-output applications. To design an efficient IPT system, the loosely coupled transformer is the key component whose design and interaction with other system components can be difficult to formulate. In this paper, a systematic design methodology for an efficient IPT LED lighting system is proposed. The analysis, implementation, and verification are detailed.

Maximizing DC-to-Load Efficiency for Inductive Power Transfer

Inductive power transfer (IPT) systems for transmitting tens to hundreds of watts have been reported for almost a decade. Most of the work has concentrated on the optimization of the link efficiency and has not taken into account the efficiency of the driver. Class-E amplifiers have been identified as ideal drivers for IPT applications, but their power handling capability at tens of megahertz has been a crucial limiting factor, since the load and inductor characteristics are set by the requirements of the resonant inductive system. The frequency limitation of the driver restricts the unloaded Q-factor of the coils and thus the link efficiency. With a suitable driver, copper coil unloaded Q factors of over 1000 can be achieved in the low megahertz region, enabling a cost-effective high Q coil assembly. The system presented in this paper alleviates the use of heavy and expensive field-shaping techniques by presenting an efficient IPT system capable of transmitting energy with a dc-to-load efficiency above 77% at 6 MHz across a distance of 30 cm. To the authors knowledge, this is the highest dc-to-load efficiency achieved for an IPT system without introducing restrictive coupling factor enhancement techniques.

Design Methodology for High Efficient Inductive Power Transfer Systems With High Coil Positioning Flexibility

With contactless inductive power transfer (IPT), it is possible to transfer electrical energy to stationary or movable consumers without contacts, cables, or slip rings. To reduce the very high development effort of new contactless inductive energy supplies, a new systematic and modular design methodology is presented in the paper. This methodology includes new methods to increase the transfer efficiency and the positioning flexibility of the consumer device and is particularly implemented into a simulation software tool. The positioning tolerance is improved by the optimization of the coil and ferrite geometry. Thereby, the influence of physical and geometrical parameters on the magnetic coupling and on the electrical transfer characteristics is investigated. As a result of the design methodology, a new IPT system for household appliances in the output power range of 1 kW at an overall efficiency of more than 90% and with a high positioning tolerance is presented.

Novel Method for Selective Nonlinear Flux Guide Switching for Contactless Inductive Power Transfer

Efficient inductive power transfer has become an area of increasing scientific interest as it can solve some problems associated with traditional wired or contact power transmission. These include but are not limited to corrosion, mechanical friction, clutter and impracticality in places like underwater and subterranean applications. This wireless energy transfer is made possible by the optimization of electromagnetic induction, circuit frequency resonance all achieved with advanced power electronics. One of the components of this technology is the precise delivery of the incident electromagnetic fields to the precise location to which they are converted to power via induction, without indiscriminate emission of these electromagnetic fields inefficiently into the surrounding areas. This paper presents a method in achieving bounded spatial freedom using flux-guide saturation for flux delivery to one or more secondary coils for contactless inductive power transfer. The experiments demonstrate the principle of using the nonlinearity of a ferrite flux shield in order to “open up” a flux path from the primary to the secondary coil to achieve inductive power transfer.